Packaging Guidelines for MinGW Cross Compilers

Future GuidelinesThese guidelines are active as of Fedora 17. For older Fedora releases (including RHEL-6 and older) the old guidelines still apply which can be be found here: Packaging:MinGW_Old

Introduction

The Fedora MinGW project's mission is to provide an excellent development environment for Fedora users who wish to cross-compile their programs to run on Windows, minimizing the need to use Windows at all. In the past developers have had to port and compile all of the libraries and tools they have needed, and this huge effort has happened independently many times over. We aim to eliminate duplication of work for application developers by providing a range of libraries and development tools which have already been ported to the MinGW cross-compiler environment. This means that developers will not need to recompile the application stack themselves, but can concentrate just on the changes needed to their own application.

As of Fedora 17 a set of RPM macros and packages have been introduced which help packagers compile binaries for multiple targets. The targets Win32 and Win64 are supported.

Track Fedora native package versions

In general terms, cross-compiled MinGW versions of packages which are already natively available in Fedora, should follow the native Fedora package as closely as possible. This means they should stay at the same version, include all the same patches as the native
Fedora package, and be built with the same configuration options.

The MinGW SIG have written an RPM comparison tool which makes it possible to compare cross compiled MinGW packages with the Fedora native packages, in order to determine whether versions, patches and configuration are aligned.

Package naming

MinGW source packages should be named by prefixing the Fedora native package name with mingw-. The packages generated from this should be prefixed according to which platform they're being built for:

mingw32-

Used for packages which are built for Win32

mingw64-

Used for packages which are built for Win64

Binary packages always specify platformThis means that there should never be built binary packages which are simply named mingw-. The binary package names should all specify their platform. This is achieved by having %files -n mingw32-foo and %files -n mingw64-foo section but not a %files section.

Base packages

The base packages provide a root filesystem, base libraries, binutils (basic programs like 'strip', 'ld' etc), the compiler (gcc) and the Win32/Win64 API. Packages may need to depend on one or more of these. In particular, almost all packages should BuildRequire mingw-filesystem, mingw32-gcc and mingw64-gcc. The correct Requires flags will get added automatically when the __find_requires macro is overridden (as will be described later on in these guidelines)

Win32 and Win64 API. A free (public domain) reimplementation of the header files required to link to the Win32 and Win64 API. No direct equivalent in base Fedora - glibc-devel is closest

Build for multiple targets

The goal of the MinGW framework is to provide an easy way for package maintainers to build their packages for multiple targets using one .spec file. To aid developers in this several RPM macros have been developed which are part of the mingw-filesystem package.
These RPM macros will be explained later on in these guidelines.

Several RPM macros depend on the package name minus the prefix, so each package must contain %global mingw_pkg_name foo (where foo is the name of the package, for example glib2)

To indicate which targets should be build, the package must contain at least one of the following lines:

%global mingw_build_win32 1

Build for the Win32 target

%global mingw_build_win64 1

Build for the Win64 target

One source RPM, separate binary RPMs per-target

Each cross compiled MinGW package which builds binaries for a specific target should put the binaries for that target in a separate subpackage. So if a package foo builds binaries for the Win32 and Win64 targets, then the source RPM should provide two subpackages named mingw32-foo and mingw64-foo.

The main package (mingw-foo in our example) must have Requires: xxx tags for all the targets. To aid in this, the RPM macro %{?mingw_default_requires} should be added to the spec file.

This means that a spec file must contains %package and %files sections for all the targets.

If a package contains translations then all calls to the %find_lang must be replaced by %mingw_find_lang.
This causes all translation filelists to be split in per-target filelists.
For example: when a spec file contains something like this:

The same also applies for the x86_64 target. This target uses 'x86_64-w64-mingw32' as prefix instead of 'i686-w64-mingw32'

Naming of the root filesystem

The root filesystem contains Windows executables and DLLs and any other Windows-only files. It is necessary both because we need to store Windows libraries in order to link further libraries which depend on them, and also because MinGW requires a root filesystem location.

The location for Win32 target is provided by the macro:

%{mingw32_sysroot} %{_prefix}/i686-w64-mingw32/sys-root

And the Win64 target is provided by the macro:

%{mingw64_sysroot} %{_prefix}/x86_64-w64-mingw32/sys-root

Standard mingw RPM macros

The mingw-filesystem package provides a number of convenience macros for the cross compiled sysroot directories, and
toolchain. It is mandatory to use these macros in all MinGW cross compiled packages submitted to Fedora.

Toolchain macros

The following macros are for the %build and %install section of the spec

Generic macros:

mingw_cmake

Call the cmake binary for all the configured targets (mingw_build_win32/mingw_build_win64)

mingw_configure

Call the configure command for all the configured targets (mingw_build_win32/mingw_build_win64)

mingw_make

Call the 'make' command for all the configured targets (mingw_build_win32/mingw_build_win64)

mingw_make_install

Call the 'make install' command for all the configured targets (mingw_build_win32/mingw_build_win64)

Filesystem location macros

The following macros are for use in %build, %install and %files sections of the RPM spec

For the Win32 target:

mingw32_bindir

%{mingw32_prefix}/bin

Location of Windows executables.

mingw32_datadir

%{mingw32_prefix}/share

Shared data used under Windows.

mingw32_docdir

%{mingw32_prefix}/share/doc

Documentation.

mingw32_infodir

%{mingw32_prefix}/share/info

Info files (see note below).

mingw32_includedir

%{mingw32_prefix}/include

Header files used when cross-compiling for Windows.

mingw32_libdir

%{mingw32_prefix}/lib

Windows libraries (see sections below).

mingw32_libexecdir

%{mingw32_prefix}/libexec

mingw32_mandir

%{mingw32_prefix}/share/man

Man pages (see note below).

mingw32_prefix

%{mingw32_sysroot}/mingw

Windows equivalent of %{_prefix}, required by MinGW.

mingw32_sbindir

%{mingw32_prefix}/sbin

mingw32_sysconfdir

%{mingw32_prefix}/etc

Configuration files used when running under Windows.

mingw32_sysroot

%{_prefix}/i686-w64-mingw32/sys-root

Windows system root.

For the Win64 target:

mingw64_bindir

%{mingw64_prefix}/bin

Location of Windows executables.

mingw64_datadir

%{mingw64_prefix}/share

Shared data used under Windows.

mingw64_docdir

%{mingw64_prefix}/share/doc

Documentation.

mingw64_infodir

%{mingw64_prefix}/share/info

Info files (see note below).

mingw64_includedir

%{mingw64_prefix}/include

Header files used when cross-compiling for Windows.

mingw64_libdir

%{mingw64_prefix}/lib

Windows libraries (see sections below).

mingw64_libexecdir

%{mingw64_prefix}/libexec

mingw64_mandir

%{mingw64_prefix}/share/man

Man pages (see note below).

mingw64_prefix

%{mingw64_sysroot}/mingw

Windows equivalent of %{_prefix}, required by MinGW.

mingw64_sbindir

%{mingw64_prefix}/sbin

mingw64_sysconfdir

%{mingw64_prefix}/etc

Configuration files used when running under Windows.

mingw64_sysroot

%{_prefix}/x86_64-w64-mingw32/sys-root

Windows system root.

Compilation of binaries

In order to build binaries for multiple targets we have to call commands like ./configure and make multiple times (once for each target).
If one has to write this all out in a spec file then it will lead to duplicate code.
To reduce the amount of duplication, several RPM macros have been introduced to help with the compilation.
These macros are %mingw_configure, %mingw_cmake, %mingw_make and %mingw_make_install

These macros use out of source compilation to build binaries for all the targets.
Almost all packages support out of source compilation or require slight patching. The only known exceptions to date are zlib and openssl.
Packages which don't support out of source compilation may require a different approach like performing everything in the %install phase.
If you happen to stumble across a package which requires a different approach feel free to contact us on the Fedora MinGW mailing list

There's a difference in the behavior between these macros and the original %{mingw32_xxx} macros.
As all commands will get executed multiple times (once for each target) arguments to the macros cannot be given if the macro is in curly braces (%{}). One has to invoke the macro without curly braces for things to work. For example, with the original Fedora MinGW toolchain you could do:

%{mingw32_configure} --disable-xlib --enable-win32

This has to be changed to something like this:

%mingw_configure --disable-xlib --enable-win32

Note that the '{' '}' characters need to be omitted from the mingw_configure macro in this case.

Some packages need to be built multiple times for each target. Examples of this are packages which have to be built once for a static version and once for a shared version.
Such packages can add a custom suffix to the build directory used.
Say you've got something like below:

Most packages used the command make %{?_smp_mflags} to build the package.
In the MinGW cross compiler framework you have to use %mingw_make %{?_smp_mflags} to build the package for all configured targets
As with the %mingw_configure macro you can also use the -s argument to indicate a custom suffix to the build directory used

To install the package the command make install DESTDIR=$RPM_BUILD_ROOT was used in almost all cases.
This can be rewritten to %mingw_make_install DESTDIR=$RPM_BUILD_ROOT to install the package for all configured targets
The -s argument can also be used here

Some packages require some custom instructions before the files are ready to be packaged. Such code can remain as is. However, you may need to duplicate these instructions multiple times (for all configured targets).

Dependencies

If a package contains binaries which depend on a DLL provided by another package, these dependencies should be expressed in the form:

mingw32(foo.dll)

where foo.dll is the name of the DLL. The name must be converted to lowercase because Windows binaries contain case
insensitive dependencies. The form 'mingw32(foo.dll)' should be used for Win32 binaries and the form 'mingw64(foo.dll)' for Win64 binaries.

Correct dependency generation is done automatically. Packagers should include these lines in all library packages:

All binary packages should depend on mingw32-filesystem or mingw64-filesystem (depending on the files in the package). If the lines mentioned above are used then it will be added automatically, so you don't have to add it yourself

All specfiles should BuildRequire at least:

BuildRequires: mingw-filesystem >= minimum-version

and any other BuildRequires that they need.

Build architecture

All packages should have:

BuildArch: noarch

unless they contain Fedora native executables.

Libraries (DLLs)

All libraries must be built as DLLs.

Because of the peculiarity of Windows, DLLs are stored in the %{mingw32_bindir} directory, along with a control file in
the %{mingw32_libdir} directory. For example, for a library called foo there would be:

The foo.dll file is the main library, foo.dll.a is a stub linked to applications so they can find the library at runtime, and foo.la is a libtool archive so that libtool can link to dependent libraries at build time. All of these files are required in those locations in order to link successfully. The .dll may contain a version number although not always (eg. foo-0.dll).

Do not use %{mingw32_bindir}/* or %{mingw32_libdir}/* in %files section

The %files section must list DLLs separately. Packages must NOT use %{mingw32_bindir}/* or
%{mingw32_libdir}/*

The reason for this is that libtool is very fragile and will give up on building a DLL very easily. Therefore we force the name of the DLL to be listed explicitly in the %files section in order to catch this during RPM builds.

Manpages and info files

If manpages or info files are simply duplicates of equivalent documentation found in Fedora native packages, then they should not be
packaged in the MinGW package.

Stripping

Libraries and executables should be stripped. This is done correctly and automatically if the spec file includes these lines:

%global __strip %{mingw_strip}
%global __objdump %{mingw_objdump}

(Note that if __strip and __objdump are not overridden in the specfile then this can sometimes cause Windows binaries to become corrupted).

Debuginfo subpackage

Most binaries contain debugging symbols when the package gets built. To split the debugging symbols to a separate debuginfo package (as is done with native Fedora packages) the spec file must include these lines: